Fig. 1. Gross phenotype of headshrinker mutants. (A-H) External views (A,B) and skeletal specimens (C-H) of wild-type (A,C,E,G) and headshrinker (hsk) mutant (B,D,F,H) P0 neonates. Higher magnification views of the head region of C and D (C',D'), sternum (E,F) and vertebral bones (G,H). Arrowheads and asterisks in E,F indicate asymmetrical attachment of ribs to the sternum, and anteroposterior dislocation of the sternum, respectively; arrowheads in H indicate bifurcation and/or fusion of ribs. (I-P) The external morphologies of wild-type (I-L) and hsk mutant embryos (M-P). The arrowhead in N indicates the abnormality in the anterior neural folds. (Q) Phenotypic variability of hsk mutants. Sections of wild-type (R) and hsk mutant (S) embryos; asterisks indicate somites. c1, atlas; e, exoccipital bone; f, frontal bone; i, interparietal bone; mn, mandible; mx, maxilla; n, nasal bone; nt, neural tube; p, parietal bone; pm, premaxilla; s, supraoccipital bone. Scale bar: 5 mm in C,D; 1 mm in C',D'; and 20 µm in R,S.